US1596459A - Propeller pump - Google Patents

Description

Aug. 17 1926. 1,596,459

H. F. SCHMIDT PROPELLER PUMP Original Filed June 9. 1924 4 Sheets-Sheet 1 h'. fchmidt Wl NES S INVENTOR yg l BY $7 09W ATTORNEY Aug; 17 192e. 1,596,459

H. F. SCHMIDT PROPELLER PUMP A original Filed June 9. 1924 4 sheetssheet 2 H. /'Sahmidf WITNEssEs; lNvENToR l' BY ATTORNEY Aug. 17 1926.

H. F. SCHMIDT PROPELLER PUMP Original Filed June 9. 1924 2Q 4o in BU non 4 Sheets-Sheet 3 RATID or Ptonscvsv T0 msc AIEAL' l Z El 4 5 RATIO 0F FITCH RATIOS ga l0.

NUMBER oF BLAvEa on PRoPElLcn 6FT ll.

H. f.' .Schmidt l INVENTOR ATTORNEY Aug. 17 1926. 1,596,459

H. F. SCHMIDT PHOPELLER PUMP o-iginnl Filed June 9` 1924 4 shuts-sheet 4 fl. ESC/70712!! WITNESSES: INVENTOR l' BY ATTORNEY Patented Aug. 17, 1926.

HENRY F. SCHMIDT, 0F LANSDO ELECTRIC & MANUFACTURING C0.,

WNE, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE A CORPORATION OF PENNSYLVANIA.

IPROPELLER PUMP.

Application llled. June 9, 1924, Serial No. 718.906. Renewed .Tune 25, 1926.

This application of my application, April 6, 1920, and i Serial No. 573,050,

is a continuation in art Serial N o. 371,648, led n part of my application, filed July 5, 1922.

This invention relates to propeller pumps and it lias of this type which for an object to produce a pump is simple in construction and is more efficient than similar pumps noW in use-and known to me.

A further object pump in which the spacing of the disk area of the the blades, ratios of the blades, portions of the fluid is to produce a propeller propeller, the axial pitch and the areas and propassages of the pump casings are so proportioned and co-related as to produce a pump in which losses, due to shock and cavitation nated.

These and other de more apparent throughout the further are substantially elimiobjects, which will be description of the invention, are attained by means of`a pump embodying the features herein described and illustrated.

In the drawings accompanying and forming a part hereof Fig. 1 is a somewhat diagrammatic longitudidnal sectional view of a propeller pump embodying my invention. Fig. 2 is a side elevation of a propeller embodying features of my invention and forming a detail of the Fig. 1. Fig. 2Ll is propeller shown in elusive, are diagrammatic views apparatus illustrated in an end elevation of the Fig. 2. Figs. 3 to 8ingraphically illustrating principles employed in pumps cally setting forth invention.

Figs. 9, 10 and 11 ves or diagrams graphifeatures of pumps em.- Figs. 12 to 15, in-

clusive, are diagrammatic views explanatory of principles involved in my invention. Fig.

1G 1s a diagrammatic view showing the effect of the vena contracta propeller design.

(zo-efficient upon the Throughout the further description of my invention I have employed the in its broad sense, gases and liquids,

word fluid that is, to include both and the term pump is employed in its broad sense, since I do not desire to limit my invention to pump for use in connection with non-compressible fluids.

leferiing to the In Figs. 1 and 2 drawings I show more or less diagrammatically a practical arrangement of a propeller pump embodying my invention. The pump includes a casing 15 provided Witli an inlet port 16 and a delivery port 17. As is usual in pumps of this character, the fluid delivery passages converge from the inlet port 16 to a throat at which the propeller is located. This convergence is for the purpose of reducing the velocity of flow at the inlet and incidentally occasions an increase in velocity of How at the throat such that, under normal operating conditions,the fluid is moving at substantially the axial discharge velocity when acted upon by the propeller. The casing is also shown provided with a divergent outlet which extends from the throat to the port 17. This is also a usual construction and occasions a velocity conversion by which the kinetic or velocity energly of the fluid leaving the propeller is trans ormed into potential energy in the form of pressure.

The propeller 18 is shown mounted on a shaft 19 which extends through a suitable journal formed integrally with the casing 15 and provided at one end with a suitable packing 20. The ropeller illustrated is provided with two b ades 21 and, as has been said, is located at the throat formed by the convergin -diverging fluid passages of the casing. T e hub portion 2la of the propeller is tapered from the inlet to the outlet side of the propeller so as to occasion an additional contraction of the stream lines as the fluid passes through the propeller. In addition to this the tapered hub is employed for the purpose of preventing aphenomenon analogous to that occasioned Vby obstructing the free flow to all sides of an orifice. This is ordinaril termed a suppressed orifice where the ow of one or more sides of the orifice is prevented by the proximity of a Wall or diaphragm. In the drawings I have shown a stationary cone or tail piece 22, which, in effect, forms a continuation of the hub portion and is held in place by the directing varies 23. The tail piece is so proportioned that it forms one wall of the diverging annular passage between the propeller and the outlet port 17. The directing varies 23 are so designed and so located that they re-direct the Huid issuing from the propeller and deliver it in a direction substantially parallel to the axis of the propeller. It will be apparent that the vanes areemployed primarily for the purpose of converting the rotary velocity of the fluid leaving the proller into effective velocity along lines parallel to the axis of the propeller. These vanes are so proportioned and disposed that the inlet edges are substantially tangential to the lines of flow leavin the propeller and the fluid is gradually de ected so that the change is accomplished with no shock and a minimum loss occasioned by surface friction.

For the purpose of maintaining substantially uniform flow throughout the inlet passages, I employ directing diaphragme 25 which sub-divide the inlet into at least two sections. These diaphragme are so formed and disposed that they conform closely to the lines of fluid ilow, and by dividing the flow, occasion less variation in velocity past points defined by any transverse plane, than would be the case if no diaphragms were employed. The pro eller pump shown in the drawings comprises a casing of the el bow type, one leg of which constitutes the entrance leg and the other lea` o'f which is provided with convergin and diverging portions and constitutes t e pumping leg.

The casing is provided with an inwardlyprojecting bearing 19' which is in axial alignment with the pumping leg referred to and which su ports a drive shaft 19 extending externa y of the casing, the propeller 21 being secured to one end of the drive shaft so that it is supported in an overhung manner. The hub portion 21 of the propeller is arranged adjacent to one end of the bearing 19 and its external surface, in eiect, constitutes a continuation of the external surface of said bearing. fairing cone or tail piece 22 is arranged at the discharge side of the propeller with its base adjacent to the hub portion 21 so that its external surface in e'ect constitutes a continuation of the external surface of the hub portion 21. The fairing cone or tail piece 22 is supported by directing vanes 23 which serve to correct for the angular discharge of fluid by the propeller, that is, these guide vanes gradually change the direction of flow of the stream from the propeller so,

that it assumes a direction of flow axially of the diverging ortion.

The prope er is so formed that the projected area of the blades is materially less than the annulus area thereof, thereby avoiding the undesirable effects of interfering stream lines in the fiuid and resulting eddies at the inlet side of the propeller. The term projected area as applied to the blades of the roieller indicates the projected area of the Ela the axis of rotation of the propeller. The term annulus or disk area is used herein to designate the area of the annulus defined es upona plane perpendicular to by the outer peripheral face of the hub 21 and the outer tips of the rotating blades 21. The hub 21'* is shown as being tapered; and, in determining the annulus area, the large diameter must be considered as defining the inner circle of the annulus. If the hub should be cylindrical, then the diameter thereofwould define such inner circle. The radial itch of the blades Vis constant. As the axial) pitch of each blade increases from the inlet or leading edge to the outlet forA trailing edge, the plitch ratio of the trailin edge is greater t an the pitch ratio of the leading edge. This increase of pitch serves to accelerate the fluid as it traverses the propeller to compensate both for the increase in velocity due to the contraction of the stream as it approaches and traverses the propeller and to the discharge of fluid by the propeller at an angle. By the term itch ratio as herein employed is meant t e ratioV of the pitch of a blade at any point to the diameter of the propeller. For example, assuming a propeller having a 12 inch diameter and a pitch of 9 inches at its leading edge and a pitch of 18 inches at its trailing edge, then the pitch ratio of the 12 and of the trailing edge leading edge is The ratio of pitch ratios of the trailing edge to the leading edge is, in this illustration, divided by .which is equal to 2.

In constructing pumps embodyin my invention, I take cognizance of the 'act that all particles of a fluid ilow along lines of A least resistance toward the point of least pressure in the body of the fluid. The convergence of the stream lines set up within a cates that the iuid approaches the orifice from all possible directions and that the convergence of the stream lines Within the body of the Huid continues even after the jet is formed. I, therefore, recognize the fact that the movement of the blades of a propeller through the fiuid acted upon occasions a low through the body of the fluid along stream lines which converge toward the source of thedisturbance, or, in other words, extend in a direction parallel to the axis of rotation of the blades'of the pro` peller. I also reco ize the fact that the rotary motion of t e propeller blades delects the direction of flow of the iuid, thereby occasioning a flow in a substantially helical path, and that this causes a further contraction of the streams of fluid. I also bear in mind that the blades are acting upon a fixed column of fluid or, in other words, I recognize the condition occasioned by the fact that the fluid acted upon is confined by the pump casing prior to, during, and after the fluid has been subjected to the direct action to the propeller blades. All these facts are taken into account in the construction and design of pumps embodying my invention, and I have so constructed the pump that a co-relation of the different principles employed in its design is obtained in such a Way as to occasion a minimum loss in the transfer of' energy from the propeller to the fluid acted upon, and in the conversion of the velocity energy of the fluid to potential or pressure energy.

Referring to the drawings:

Fig. 3 is a diagrammatic illustration of a sharp-edged orifice. The vena contracte of the jet of fiuid'issuing from the orifice as Well as the stream lines which produce this contraction of the jet are illustrated. It is well known that the vena contracta evidences the fact that stream lines are set up in the entire body of the confined fluid and that these stream lines tend to converge toward the center of the orifice.

In Fig. 4, I have diagrammatically illustrated a thin, flat plate submerged in a body of fluid. By considering the flow occasioned under conditions illustrated in Fig.`

3, it will be ap arent that a transverse movement of the p ate 8 in the direction of the arrow Will occasion a condition, so far as stream lines are concerned, which is similar to the condition graphically illustrated in Fig. 3. A uick transverse movement of' the plate in t e direction of the arrow will tend to create a vacuum immediately back of the plate and will occasion a flow of fluid Within the body in an attempt to fill or prevent the vacuum created by the movement of the plate. This flow is along stream lines Within the body of fluid similar to stream lines formed by the issuance of fluid through the sharp-edged orifice and the conditions of flow Will be very similar, since in Fig. 3, the flow is occasloned by a reduction in pressure occasioned by the orifice, and in Fig. 4, the flow is occasioned by a reduction in pressure within the body of the liquid occasioned by the transverse movement of the late. It will be apparent that the entire ody of fluid Will be more or less affected by the displacement occasioned by the movement of the plate and that the fluid behind and immediate] adjacent to the plate will flow at a velibcity substantially equal to the velocity of the plate and that the stream lines set up Will converge toward" the plate, the tendency, of course, being for the liquid to move along lines of least resistance toward the incipient vacuum occasioned by the movement of the plate.A It

will, of course, be apparent that cavitation may not actually take place, but the effect of the movement of the plate will be the same Within the body of fluid and will differ only in degree if cavitation does actually take place.

Fig. 4, therefore, illustrates that a transverse movement of the plate through a body of' fluid will set up converging stream lines throughout the body and that the convergence of' these streamlines is toward the origin of the disturbance, in this case, the plate, and that the velocity of the flow in the converging stream lines will increase as the streams converge and that a maximum velocity Will be reached at a point immediately adjacent to the moving plate.

`In Fig. 5, I have diagrammatically illustrated two plates 8 and 8 submerged in a body of fluid and adapted to be simultaneously moved through the fluid in lines parallel to each other and in directions indicated by the arrows. It will be apparent that the movement of each plate Will occasion a disturbance or a local drop in pres- Vsure Within the body of fluid and will thereby set up lines of flow throughout the body which will conflict with the lines of flow set up by the other plate." While it would be impossible to so space the plates that the flow occasioned by the displacement of one plate would not interfere to some extent with the flow occasioned by the displacement of the other plate, it will be apparent that the spacing of the plates may be such that under certain conditions of displacement, the lines of flow, while interfering, will not interfere to such an er: ent as to occasion eddy currents which Will appreciably reduce the efficiency of the plates in their function of creating two well-defined and substantially parallel streams Within the body of' the liquid. It will be apparent that thc plates may be so spaced that under certain conditions of displacement each plate will starve the other. By this I mean each plate may be so spaced that it will prevent the flow of liquid to the point of low pressure occasioned by the movement of the other plate. In Fig. 5, I have graphically illustrated the direction of the lines of flow occasioned by the movement of the two plates 8 and 8 and it will be apparent that a portion of the body of fluid is directly subjected to the influence of both plates, Whereas the intensity of this double influence decreases and is almost nil in that portion of the body of the fluid located between adjacent ed es of the plates. From the above, it will e apparent that the spacing of the blades of a propeller may be such that their cooperation will set up conflicting streams of lines of flow which will prevent each blade from operating effectively on th'e liquid or fluid and that on the other hand the Spacing may be such that the blades will, in eil'ect, operate independently and consequently with no appreciable detrimental effect on each other. In other Words, there may be a negative cooperation between the plates such that each plate will operate effectively in the production of a stream of liquid or fluid and will exert little or no detrimental effect on the operation of the other plate.

In Fig. 6, I have illustrated a plate 8 submerged within a body of fluid and moving in the direction of the arrow l0. It will be noted that the direction of the motion of the plate is at an angle lesss than 90 to the face of the plate. Under such conditions, a movement of the plate from the position CD to the dotted line position EF will accomplish the same effect, so far as displacement in the direction of'the arrow llv is concerned, as if a plate having the width- GD, and a length equal to that of the plate 8a had been moved from the position indicated by the dotted line GD in the direction of the arrow 1l to a position CF. In other words, the movement of a plate through a liquid or fluid in a direction at an angle less than a right angle to the plane of' the face of the plate will occasion a displacement in any direction within the body of fluid which will be proportional to the projected area of the plate on a plane at right angles to the direction of the displacement under consideration. Such a displacement will also set up stream lines Within the body of the fluid substantially similar to the stream lines diagrammaticall illustrated in Figs. 4 and 5, and the velocity along these stream lines in the direction of the displacement under consideration will increase with the convergence of the stream lines and will reach a maximum velocity at the trailing edge of the moving plate. It will however, be apparent that the stream lilies so produced will be influenced both by the direction of motion of the plate and the position of its effective face. In other words, the stream lines set up within the body of the fluid wiil be inclined with relation to both the arrows 10 and 1l and the stream of fluid leaving the plate will, therefore, be deflected an amount depending upon the motion of the plate and the angular position of the plate with relation to its direction of motion. This deflection of the stream lines occasions a reduction in the cross sectional area of the stream; and, as a result, the velocity of flow within the deflected stream is materially increased over that of the fluid moving toward the` plate, since the area times the flow must in both cases be equal.

It will be apparent that the deflection of the fluid leaving the plate 8'* must be occasioned without shock. This means that the direction of the lstream lines of the fluid `approaching the plate must conform to the direction of the stream lines of the yfluid leaving the plate. Under such conditions, the change of direction will be gradual and the stream lines leaving the plate will, in effect, be a continuation of those approaching the plate with the result that gradual change in direction will be accomplished along curved stream lines both in the fluid approaching and in the fluid leaving the plate. In addition, these curved stream linesl will converge both by reason of the vena contracta efi'ect illustrated in Figs. 3 and 4, and the change of direction of flow, illustrated in Fig. 6. In order to produce a gradual acceleration of the fluid, without subjecting it to shock,

1t is necessary that the relative motion of the fluidand the plate should be such that the fluid approaches the Working face of the plate along lines which are substantially parallel to the surface of the plate at the entrance or leading edge. It will, however, be apparent that with such a condition of relative motion Vbetween the fluid and the plate, the plate would have no propelling effect on the fluid and consequently it is necessary to so arrange the surface of the plate that the angle of the surface with relation to the direction of motion of the plate will increase from the leading to the rear or trailing edgeof the plate. It is also necessary that this increasing pitch be so proportioned that the fluid will be gradually accelerated a sufficient amount to compensate for the convergence of the stream lines occasioned by the vena contracta effect and the change in direction of flow.

The fact that the vena contracta of a jet has an arca which is less than that of the orifice of its origin indicates that the velocity of flow at the vena contracta is greater for the reason that for the flow of fluids in a conduit, velocit times area is constant. However, Where t e displacing element moves in a plane substantially atright angles to the axis of the approaching column of fluid, as is illustrated in Fig. 6, the deflection of the stream occasions a still further convergence of the stream lines; and, consequently, the latter convergence occasions an increase in the velocity of flow which is greater than that occasioned by the reduction in area at the vena contracta.

The propeller blades of my improved pump must, therefore, have an increasing axial pitch, or such a ratio of pitch ratios of the trailing edges with respect tothe leading edges of the blades, so that in acting upon the fluid they will occasion a velocity of flow which is greater than that occasioned by the contraction of the stream as it traverses the propeller and by the change of direction of flow of the fluid discharged from the propeller. Also the ratio of projected blade area to the annulus or disk area should be such as to secure an undivided and homogeneous discharge so as to completely fill the rasing and avoid losses due to eddying or shock. As the area ratio is inversely proportional to the ratio of pitch ratios, the propeller blades are spaced apart suiiiciently so that no substantial loss is involved duc to stream line interference in the fluid approaching the blades. Experiments indicate that the angular deflection of Ydischarge may vary, for example, from 15 to 30P with respect to the axis of the approaching column.

In Fig. 7, I have section o-f a propeller tion is taken along illustrated a developed blade in which the seca cylindrical surface midway between the root and tip of the blade. I have also illustrated diagrammatically the direction of the lines of flow occasioned by moving such a blade through a Huid or liquid in the direction of the arrow associated with the figure. The blade l2, illustrated, increases in axial pitch from the leading to the trailing edge in accordance with the empirical rule above set forth. In Fig. 8, I have shown a similarly developed section of a pump propeller having two such blades and I have diagrammatically illustrated the lines of flow occasioned by `auch a propeller where the direction of rotation is indicated `by the arrow. Lines AA and BB associated with Fig. 8, indicate the common surface of cleavage in developing the section.

In Fig. 8, I show a pump propeller which 1s provided with two or more blades and it will be apparent that the projected area of the blades should be such as to avoid the effect of fiow interference at-the inlet side. lVith respect to the number of blades which the propeller should have, I have experimentally determined that the best elliciency is obtained with the fewest blades and that the eiiicienc'v decreases by about 4.5% for each additional blade where the ratio of pitch ratios and the ratio of projected to disk areas remain constant.

In accordance with my invention, the ratio of projected blade to disk areas varies with the contraction co-eiicient and the ratio of pitch ratios of the trailing edges with respect to the leading edges of the blades varies inversely with the area ratio. For low discharge pressures or heads, the value of the contraction co-eliicient is usually 'given as 0.625; however, as has been experimentally determined, the contraction co-eflicient increases with the discharge pressure or head. Therefore, in desi ing my propeller pump, first of all, the discharge pressure or head is takeninto consideration in correctly determining the rojected area ratio and the ratio of pitch ratios.

Assuming, by Way of example, that the contraction co-elficient is 0.625, for low discharge pressure or heads, it will be apparent that the velocity of liow is in the ratio cient, the angularity or pitch of the displacing surface must be such that its trailing edge will, in acting upon the fluid, oc-` clasion a velocity of flow which is greater t an and in addition be such as to .occasion an increase in flow which is greater than the combined acceleration required by the vena contracte. and by the change of direction. On the basis of a value of 0.625 for the vena contracte, the above theory indicates that theV pitch of the trailing edge should at least be equal to or greater than 1.85 times the pitch of the leading edge. Experiments which I have conducted indicate that the pitch of the trailing ed e should actually be about 2 to 2% times that of the pitch of the leading edge. This discrepancy is probably accounted for by friction and edge losses which are ditlicult to estimate with theoretical accuracy. The increase in pitch just described is in an axial direction with relation Vto the propeller, since the radial pitch of the blades is constant.`

Figs. 9, 10, and 11 are illustrative of certain experiments which I have conducted. In these experiments, a lovi7 head or back pressure Was involved and the generally accepted contraction co-etlicient of 0.625 was used.

In Fig. 9 for a vena contracte. co-eflicient of 0.625, the curve shows that the maximum eliciency was attained with blades having a projected area ratio of approximately 60%; however, it is to be understood that the projected area ratio may vary, such ratio being dependent upon the relative area required to secure an undivided and homogeneous dischar e which completely fills the pump casing or a ratio of pitch ratios of the trailing edges with respect to the leading edges of the blades necessary to accelerate the fluid traversing the propeller in order to compensate for velocity increases occasioned by the contraction of the stream and by the discharge thereof at an angle.

Fig. l() indicates the variation 1n elliciency occasioned by employing pump propellers or having blades of different pitch ratios where the projected area remains constant. The curve indicates that the maximum efficiency was attained when the pitch ratio of the outlet or trailing edge is two and one-half times that of the leading edge.

In Fig. 11, I show the effect on the'efliciency of the number of blades, assuming that the pitch and area ratios remain constant. It will be noted that the efficiency decreases with the increase in the number of blades While apparently a maximum efficiency is obtained with a one-bladed propeller. Obviously, however, a one-bladed propeller would ordinarily not be employed because of its inherent unbalance and consequent tendency to vibration.

I desire it to be distinctly understood that the diagrams in Figs. 9, 10, and 11 are merely illustrative in nature and were determined experimentally for aloW discharge pressure or head; and, accordingly, I do not desire to be limited to the exact proportioning of parts indicated lthereby, as. there are many factors entering into the action of propeller pumps and tending by their action and inter-action to slightly shift the salient points of these operating curves 1 n one direction or the other. For example, if the contraction co-eliicient is changed, the curves would be changed accordingly.

The requirement that the ratio of projected blade area to disk area, referred to also as the area ratio, shall be suflicient to secure an undivided and homogeneous discharge is obvious from a consideration of Figs. 12, 14 and 15. Also, it will be apparent, from Fig. 12, that the ratio of pitch ratios of the trailing with respect to the leading edges of the blades varies inversely as the projected blade area to the annulus or disk area. In Fig. 12, I show diagrammatioally and in development, two propeller blades 21 having a smaller ratio of pitch ratios than the pair of blades 30. The blades 21 should have such a ratio of projected to disk area that the fluid discharged therefrom is undivided and homogeneous. Accordingly, the parallel lines indicate the stream lines of flow from the blades 21 and it Will be seen that such lines a-djoin and that the fiuid is not divided by the blades nor is the Huid discharged from one blade intercepted by the other. In like manner, the dash lines from the blades 30 indicate how these blades should be designed in order to secure an undivided and homogeneous discharge.

The importance of having the fluid discharged in an undivided and homogeneous stream is obvious from a consideration of Fi s. 14 and 15. In Fig. 14, I show a conduit 31 connected to a larger conduit 32 so as to discharge fluid abruptly thereinto. Such a construction is very inefficient as a velocity-pressure conversion device on account of the losses due to eddies, as indicated in the view. Fig. 15 shows how the apparatus shown in Fig. 14 should be modified in order to produce an efficient velocitypressure conversion device wherein little, if any, eddy losses take place. If the streams of fluid discharged from the propeller blades should not be contiguous so as to constitute an undivided and homogeneous stream, eddy losses would take place for the same reason as in Fig. 14. A consideration of Figs. 14 and 15, therefore, shows the importance not only of having the streams of fluid discharged by the propeller blades contiguous and parts of an undivided and homogeneous stream, but also the importance of having the pump casing entirely filled in avoid shock and eddy losses.

It is also characteristic of the blades of my propeller thatthe ratio of pitch ratios varies inversely as the cosine of' the angle included between the trailing edge and the plane of rotation. See Fig. 13. In this view, the blade 21, having the smaller ratio of pitch ratios, includes a smaller angle alpha between the trailing edge and the plane of rotation than the angle alpha included between the trailing edge of the blade 30 and the plane of rotation.

As hereinbefore pointed out, my invention comprises a propeller pump in Whic the ratio of projected blade area to annulus area varies with the contraction co-efficient; and, of course the ratio of pitch v ratios varies inversely with the area ratio. I have discussed the general characteristics of my improved pump, as Well 'as the pertinent theory in explanation thereof. I have also considered in detail a pump in which the contraction co-efiicient was taken as 0.625. The situation in which a larger co-elficient is involved, due to increased back pressure or head, will now be considered. In a case of this kind, preliminarily to the proper design of a pump made in accordance with my invention, it is necessary, first of Iall, to determine the back pressure or head and then to determine the ratio of projected blade to annulus or disk area, which varies with the inrease in the contraction coefiicient and therefore with the increase in discharge pressure or head. After the area ratio is determined, then in accordance with the rule that the ratio of pitch ratios of the trailing edge with respect to the leading edge v-aries inversely as the area ratio, the ratio of pitch ratios may be ascertained. If the co-efiicient of contraction increases, this means that the propeller blades are called upon to accelerate `the fluid less and less to compensate for increase in velocity due to contraction of the stream traversing the propeller.

The effect of increasing back pressures or head is illustrated by diagrammatic Fig. 16. From this view, it will be seen that, for an increase in pressure or head, the co-eicient of contraction, indicated by the curved line designated co-efiicient of contraction, increases and that the area ratio varies with the contraction co-eiicient, and that the order to hoo ratio of pitch ratios so designated) varies traction co-etlicient.

The advantages in improved eficiency attained in the employment of the pump of this invention arise from the absence of eddying currents in the stream passing to, through and from the propeller, yand from (indicated by the curve inversely with the conthe union Without shock of the separate columns of fluid projected or delivered by the separate blades ot' the propeller to form a homogeneous stream outwardly flowing from the propeller. The essential relations in the propeller construction of axial pitch and projected area to the contractional coefiicient of the stream traversing the propeller, as hereinabove fully described and set fforth in the appended claims, result in the attainment of the above indicated improved operative characteristics of the propeller pump .of the present invention.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modi cations without departing from the spirit thereo and I desire, therefore, that only such limitations sh-all be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

l. In combination in a propeller pump or fan, a propeller comprising a hub portion, blades mounted thereon and having a rojected area of approximately 60% the isk area, and an axial pitch at the outlet edge, so pro ortioned with relation to the pitch at the in et edge as to compensate for the increase in velocity due tothe contraction of the stream lines in the fluid traversing the propeller and the contraction due to the angularity of the stream lines leaving the blades.

2. In combination in a fluid impeller of the propeller type, a propeller comprising a hub portion, blades mounted thereon and having a projected area of approximately 60% the disk area, and an increasing axial pitch, the pitch ratio of the leading edge of cach blade being such as to receive the fluid without shock and increasing to a pitch ratio at the trailing edge such as to occasion an increase in velocity greater than that occasioned by the contraction of the stream lines as the fluid traverses the propeller and the contraction occasioned by the angularity of the stream lines leaving the blades of the propeller.

3. In combination ina pump, a propeller. comprising a hub portion, blades mounted thereon. having a projected area materially less than the disk area. and having an increasing axial pitch, the ratio of the pitch ratios of the trailing to the leading edge having an inverse relationship to the ratio of the projected area to the annulus or disk area.

4. In combination in a pump, a propeller, comprising a hub portion, blades mounted thereon, having a. projected area materially less than the disk area, and having an increasing axial pitch, the ratio of the pitch ratios from the trailing to the leading edge being greater than the ratio of the disk area to the projected area.

5. In combination in a comprising blades having increasing pitch from the leading to the trailing edge, the increase of pitch having a definite relation to the projected area ratio.

6. In combination in a pump, a propeller comprising blades having increasing pitch from the inlet to the outlet edge, the increase in pitch being inversely proportional to the projected area ratio of the blades and also inversely proportional to the cosine of the angle which the trailing edge of the blade makes with the plane of rotation.

In combination in a propeller pump, a propeller having a projected area materially less than the disk area and an increasing pitch from the leading to the trailing edge, the ratio of the pitch ratios being such as to compensate for the increase in velocity occasioned by the contraction of the stream lines of the fluid traversing the propeller and the contraction of the stream lines occasioned by the angularity of the stream lines leaving the propeller.

8. In combination in a pump, a casing having Working passages formed therein and a propeller mounted within said casing and aving a projected area materially less than the disk area and increasing axial pitch such that the separate streams projected by the separate blades of the propeller unite to just fill the delivery passage of the pump without shock or cavltation.

9. In combination in a propeller pump, a, casing having working passages formed therein, and a propeller located within the Working passages of the pump and having a projected area of approximately half the disk area, and an increasing pitch such that the separate streams projected by the separate blades of the propeller unite to just ll the delivery passage of the pump without shock or cavitation.

10. In combination in a propeller pump, a casing having a converging-diverging Working passage, and a propeller located at the throat of said passage, and having a projected area of approximately 55% of the disk area of the propeller and an increasing pitch from the leading to the trailing edge of each propeller blade.

11. In combination in a propeller pump, a casing having a convergingdiverging Working passage, and a two-blade propeller lopump, a propeller cated at the throat of said passage and having a projected area of approximately half of' the disk area of the propeller, and anincreasing pitch from the leading to the trailing edge of each blade.

1Q.. In combination in a propeller pump, a casing having a converging-diverging flui passage, a tWo-bladed propeller located at the throat of said passage and havin a projected area substantially less than t e disk area and an increasing axial pitch whereby the separate streams of fluid projected by eachblade unite to form a single stream substantially filling the outlet portion of said passage and homogeneous throughout as regards continuity of flow.

13. In combination in a propeller pump, a casing having a converging-diverging flui passage, a two-bladed propeller, located at the throat of said passage, and having a projected arca of substantially half the disk area.

14. In combination in a propeller pump, a casing having a converging-diverging fluid passage, a tWo-bladed propeller, located at Ythe throat of said passage, and having a projected area of approximately half the disk area, and having an increasing axial pitch.

15. In combination in a propeller pump, a casing, a ytvvo-bladed propeller located within the casing and having a projected area materially less than the disk area, and an increasing axial pitch such that the axial pitch at the trailing edge of each blade is substantially twice that at the leading edge.

16. In combination in a propeller pump, a casing, a two-bladed propeller mounted therein of constant-radial pitch and having a projected area of approximately one half the disk area and an increasing axial pitch.

17. In combination in a propeller pum ay casing having a converging-diverging uid passage, a tWo-bladed propeller mounted therein at the throat of said passage and of increasing axial pitch, the ratio of the pitch ratios from the leading to the trailing edge being substantially inversely proportional to the ratio of the projected area to the disk area.

18. In combination in a propeller pump, a casing having a converging-diverging fini passage, and a propeller mounted at the throat of said passage and having blades, the projected area of the blades being materially less than the annulus or disk area, the radial pitch of the blades being constant, and the axial pitch of the blades increasing from the leading to theitrailing edges.

19. In combination in a propeller pump, a casing having a converging-diver'ging fluid passage, and a propeller mounted at the throat of said passage and having blades, said blades having a proj mately one half the disk area, a constant ected areaapproxi-y radialpitch and an axial pitch increasing from the leading tothe trailing edges.

20. In combination in a propeller pump, a casing having a converging-diverging fluid passage, a propeller located therein at the throat of said passage and having a constant radial pitch and a projected area materially less-than the disk areal 21. In combination in a propeller pump, a casing having a converging-diverging fluid passage, a two-bladed propeller located therein at the throat of said passage, having a constant radial and an increasing axial pitch, and a projected area of approximately half the disk area.

22. In combination in a propeller pump, a casing and a propeller arranged therein, the axial blade pitch of the propeller increasing from the leading tothe trailing edges, the ratio of the pitch at the trailing edge to the pitch at the leading edge being approximately an inverse function of the pressure head at the discharge side of the propeller.

23. In a propeller pump, a propeller having blades which increase in axial pitch from the leading to the trailing edges, the ratio y"of the pitch at the trailing edge of the blade to the pitch at` the leading edge thereof being approximately an inverse function of the contraction co-eiiicient of the stream traversing the propeller.

24. In a propeller pump, a propeller having blades which increase in axial pitch from the leading to the trailing edges, the rate of increase in the blade pitch being approximately an inverse function of the pressure head at the discharge side of the propeller.

25. In a propeller pump, a propeller having blades which increase in axial pitch from the leading to the trailing edges, the rate of increase in the pitch of the blade being approximately an inverse function of the contraction (3o-efficient of the stream traversing the propeller.

26. In a propeller pump, a propeller having blades whose ratio of projected blade area to annulus or disc area is proportional to a function of the contraction of the stream traversing the propeller and Whose ratio of pitch ratios of the trailing edges of the blades with respect to the leading edges is approximately proportional to an inverse function of the area ratio.

27. Ina propeller pump, a propeller having blades Whose ratio of projected blade area to annulus or disc area is proportional to the extent of contraction of the stream traversing the propeller and whose ratio of pitch ratiosof the trailing with respect to the leading edges is approximately inversely proportional to the area ratio.

28. In a fluid impelling device, a plurality of similar blades mounted for movement in the samexpath, the projected area of said between 50% and 62.5% of the area of said blades on the surface swept over by the surface, said blades having an increasing discharge edges of said blades being bepitch from the leading to the trailing edges tween 50% and 62.5% of the area of said thereof, the ratio of the pitch ratios of the surface. leading to the trailing edge having a con- 29. In a fluid impelling device, a plu` verse relationship to said area ratio. rality of similar blades mounted for move- In testimony whereof, I have, hereunto ment in the same path, the projected area subscribed my name this 23rd day of May, of said blades on the surfacelswept over 1924. 1 by the discharge edges of said blades being HENRY F.,SCHMIDT.

the samehpath, the projected area of said blades on the surface swept over by the discharge edges of said blades being between 50% and 62.5% of the area of said surface.

29. In a fluid impelling device, rality of similar blades mounted for movement in the same path, the projected area of said blades on the surface swept over by the discharge edges of said blades being a plu- Gerticate of Correction.

in Letters Patent No. 1,596,459, of Lansdowne, Propeller Pums, an error appears in the It hereby certified that 1926, to Henry F. Schmidt,

tion as follows:

edges of the blades; and that the said Letters Patent HENRY F. SCHMIDT.

granted August 1 7, Pennsylvania, for an improvement 111 printed specification requirinor correcage 8, line 124, claim 27 after the word trailing insert the words should be read with this correction therein that the same may conform to the record of the case in the Patent Oice.

Signed and sealed this 2d day of November, A. D. 1926.

[smal WM. A. KINNAN, 4 Acting Commissioner of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,596,459, granted August 17, 1926, to Henry F. Schmidt, of Lnsdowne, Pennsylvania, for an improvement in Propeller Pumps, an error appears in the printed specification requirinff correction as follows: Page 8, line 124, claim 27. after the word trailing insert the Words edges of the blades; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Signed and sealed this 2d day of November, A. D. 1926.

[SEAL] WM. A. KINNAN,

` Acting Commissioner of Patents.

Images